AMC timing cap C87 in trc-457 and other 858, SSB chassis

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479tx
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AMC timing cap C87 in trc-457 and other 858, SSB chassis

Post by 479tx »

I noticed in the Realistic 858 radios c87 is 2.2uf and in the 139 XLR (same board) c87 is 10uf.

Anyone have any idea what this cap does to the AMC circuit? I also noticed the 139 XLR has a diode @ d23 and the TRC-457 has a 220 ohm resistor. On someone else's advice I changed the resistor to a 1n914 diode.

Curious if I should also change c87 as well, just curious what impact it has.
479tx
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Post by 479tx »

Staring at the schematic it looks like the AMC timing cap. Can anyone confirm? I've seen a guy that's written a lot about these radios claiming you want to increase the value of this cap but in almost every other radio I've seen you decrease the value of the AMC timing cap for a snappier AMC and more overall loudness/average modulation.
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Post by Goldfinger »

Yes, that is the timing/hold cap for the clipper. Of course if you bypass D21 and D22, C87 is defeated.
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479tx
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Post by 479tx »

Thank you sir!
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